1. Field of the Invention
The present invention relates to a thumb turn latch designed to be turned by the thumb and finger though an angle of 90 degrees for releasably holding the flap of a bag-like article in a closing position.
2. Description of the Prior Art
A typical example of thumb turn latch of the type described is disclosed in Italian Utility Model Registration No. 201901. The disclosed latch includes a latch body having a grip head and a cylindrical stem extending centrally from a lower surface of the grip head. The grip head has a locking ridge disposed on and extending diametrically across the lower surface. The cylindrical shank terminates in an enlarged foot having an upwardly tapering cam surface. The latch body is rotatably mounted on a retainer attached to the body of a bag-like article. The retainer includes a split sleeve rotatably receiving therein the shank of the latch body, and a crisscross groove formed in an upper surface of the retainer for receiving the locking ridge of the latch body to lock the latch body selectively in a locking and a releasing position which are angularly spaced by 90 degrees. When the latch body is held in the locking position or the releasing position in which the locking ridge is received in the crisscross groove, the lower end of the split sleeve is held in abutment with the upwardly tapering cam surface of the shank of the latch body. In this instance, due to the camming action of the upwardly tapering cam surface, the latch body is urged downwardly toward the retainer. When the grip head is turned to move the latch body from the locking position to the releasing position and vice versa, the locking ridge is released from the crisscross groove and slides up onto the upper surface of the retainer, causing the latch body to be moved upwardly. With this upward movement of the latch body, the upwardly tapering cam surface of the enlarged foot is forced into the split sleeve of the retainer, whereupon the split sleeve, which is composed of two opposing resilient thin walls, is spreaded by the cam surface. This forcible deformation of the two opposing walls of the split sleeve continues until the locking ridge is received again in the crisscross groove to lock the latch body in the releasing position.
The known thumb turn latch of the foregoing construction is however disadvantageous in that the split sleeve of the retainer is likely to be damaged or broken due to fatigue caused by repeated bending of the two opposing resilient thin walls of the split sleeve during use of the bag-like article.